Method of grease manufacture



Sept 24, 1968 w. R. cooNs, JR., ET AL 3,403,100

METHOD OF GREASE MANUFACTURE Filed Dec. 51, 1963 United States Patent O 3,403,100 METHOD OF GREASE MANUFACTURE William R. Coons, Jr., Port Arthur, and William R. Hencke, Groves, Tex., assignors to Texaco Inc., New York, N.Y., a corporation of Delaware Filed Dec. 31, 1963, Ser. No. 334,731 14 Claims. (Cl. 252-41) This invention relates to improvements in grease manufacture. More particularly, it relates to an improved method of making lithium hydroxy fatty acid soap thickened greases comprising heating and cooling steps carried out upon the grease mixture in a continuous operation.

A continuous process for making lithium hydroxy fatty acid soap thickened greases in greatly improved yields over those obtained by other continuous processes of the prior art is described by Jones et al. in their patent, U.S. 2,652,366. In the said .Tones et al. process, a slurry of lithium hydroxy fatty acid soap and lubricating oil is heated to a temperature in the neighborhood of the solution temperature of the soap and then quenched rapidly to a temperature within a critical range, by mixing it with 'a relatively large volume of recycled grease mixture at a lower temperature, and the cooled grease mixture subjected to shearing -by recycling it through a shearing means before further cooling to packaging temperature. In the preparation of a lithium lZ-hydroxystearate thickened grease, the grease mixture is heated to about 380 F. and quenched with recycled grease mixture to a temperature in about the range B30-340 F. before it is linally cooled to packaging temperature. Heating and nal cooling of the grease mixture is preferably carried out in heat exchangers of the forced film type, wherein a rapid shearing of the grease -mixture is obtained. The present invention provides a method of producing lithium hydroxy fatty acid soap thickened greases of excellent quality in a continuous operation in yields which are substantially equivalent to those obtained by the method of Jones et al, but in a much more convenient and economical manner, since it avoids the necessity for recycling a large volume of grease mixture.

The method of this invention comprises essentially heating a slurry of lithium hydroxy fatty acid soap and lubricating `oil to a temperature at least about F. above the solution temperature of the soap, cooling the molten homogeneous mixture of soap and lubricating oil thus obtained to a temperature below the solution temperature of the soap by the addition of a relatively small amount of additional lubricating oil at a temperature below about 150 F., 'and thereafter further cooling the grease mixture with shearing. The temperature to which the grease mixture is heated and the temperature and amount of the -blending oil added during the cooling are critical conditions for obtaining satisfactory yields and product quality4 by this method.

By solution temperature of the soap is meant the point at which a clear solution or mixture of soap and lubricating oil is obtained, i.e., a solution which appears clear to the unaided eye in ordinary illumination. For lithium 12-hydroxystearate thickened mineral oil base greases this point occurs at about 385 F. While the mixture of lithium hydroxy fatty acid soap .and lubricating oil is accurately described as a solution at or above this temperature, it appears that some association of the soap molecules exists in the solution and that the type of these associations is alfected in some manner by 'further heating and other treatments of the grease mixture, since such treatments of the grease mixture at temperatures above the solution temperature of the soap have very marked effects upon the yield Kand grease properties as 3,403,102() Patented Sept. 24, 1968 will appear from the experimental results shown hereinbelow.

FIG. 1 is a diagrammatic illustration of a particularly suitable system for making greases in accordance with this invention.

FIG. 2 is Ia graphic representation of the elfect of heater outlet temperature upon yield employing blending oils at two different temperatures.

Referring in more detail to FIG. 1, numeral 1 represents a charge kettle, jacketed or otherwise equipped for heating the kettle contents to an elevated temperature above about 200 F. and Ialso provided with charging means (not shown). It is very advantageously also provided with a recycle system as shown in the diagram, comprising line 2, containing pump 3, and line 4, containing shut-oif valve 5, for -circulating the kettle contents from the bottom to the top of the kettle Ias a means of obtaining rapid and effective mixing. In addition or alternatively, the kettle may be equipped with a stirrer or other agitating means (not shown). In carrying out the grease preparation, a well dispersed soapoil mixture at an elevated temperature below about 300 F., very suitably in about the range 12S-225 F., is provided in kettle 1 by charging soap and lubricating oil in suitable proportions to the heated kettle and mixing by circulating the kettle contents rapidly lfrom the bottom to the top of the kettle. The soap and lubricating oil are charged in proportions resulting in a mixture comprising about 2-20 percent of soap, and preferably about 4-15 percent of (soap, based on the weight of the mixture. The soap-oil :mixture may be obtained by saponiication in situ if desired, by carrying out the saponiication of a suitable saponiable material in the presence of all or a portion of the lubricating oil employed in the mixture, followed by heating at a higher temperature to dehydrate.

Where it is desired to carry out the process in a completely continuous manner, a soap-oil mixture may be provided continuously by any convenient method, such as by employing two or more kettles in alternate operation which are charged either with preformed soap and oil or wherein the soap-oil mixture is obtained by saponication in situ. The process may be carried out very advantageously by continuously charging oil and preformed soap in suitable proportions to kettle 1 at a rate equal to the rate at which the slurry is drawn oi through line 6, while maintaining la strong agitation of the kettle contents by recirculating through the recycle system at a rapid rate, very suitably at a rate suicient to give a complete turnover of the kettle contents within about 1 minute, and preferably within about 1/2 minute.

The soap-oil mixture passes from kettle 1 by way of line 2, containing pump 3, and line 6i, containing pump 7, to heater 10, wherein the mixture is heated to a suitably high temperature above the solution temperature of the soap. Pump 7 is a variable capacity metering pump. Pump 3 provides a positive flow to pump 7 and bypasses the surplus thro-ugh line 4. Heater 10 is preferably of a type capable of providing rapid heating of the grease mixture together with an effective shearing and dispersing action. A very suitable heater for this purpose is a Votator, wherein the grease mixture is passed under pressure through a thin annulus between a cylinder having an internal core rotating at high speed, such as at about 500 revolutions per minute, and having Scrapers which engage the cylinder wall. The heater is supplied with a high temperature heating medium such as Dowtherm. The grease mixture in heater 10 is heated to a temperature at least about 10 F. above the solution temperature of the soap, suitably to a temperature in the range from about 10 F. to about 100 F. above the solution temperature of the soap. It is most advantageously heated to a temperature in the range from about F. to about 50 F. above the solution temperature of the soap. In the preparation of lithium 12-hydroxystearate thickened greases, the grease mixture is preferably heated to a temperature in the range from about 395 to about 445 F., and most advantageously from about 400 F. to about 435 F. The grease mixture is preferably heated rapidly to the maximum temperature from a temperature below about 300 F., preferably in less than about 1 minute.

The molten grease mixture passes from heater .10 to blender 35 by way of line 12. In line 12 the grease mixture is mixed with additional lubricating oil, at a relatively low temperature, passing from storage tan-k into line 12 by way of line 21 containing pump 22 and heat exchanger 25, and line 29 containing valve 30. The use of heat exchanger is optional, since it is generally suitable to employ the oil at ambient temperatures. However, it may be desired in some cases to employ either heating or cooling of the blending oil stream as a means of obtaining the desired effect upon the yield or product quality. A heat exchange fluid of any suitable type passes through heat exchanger 25 by way of lines 26 and 27. The blending oil may suitably be at a temperature in the range from about 25 F. to about 150 F., preferably at a temperature in the range from about 50 F. to about 125 F. The oil is introduced into line 12 at a rate such that the soap base and blending oil are in a ratio from about 2:1 to about 7:1, and preferably in a ratio from about 2.5:1 to about 6.5:1 by weight. With particular advantage in some cases, the soap base and blending oil are employed in a weight ratio within the range from about 3.5 :1 to about 5.5 :1, respectively.

Blender 35 is a vessel provided w-ith agitator means of a type capable of producing thorough mixing at low shear. Mixing of this type is obtained, for example, by means of pins or spokes arranged in a helical pattern on a slowly rotating shaft which cooperate with a row of stationary pins or spokes mounted in the wall of the vessel. The blender shaft speed is suitably in the range from about 50 to about 150l revolutions per minute. Residence time of the grease Imixture in the blender is ordinarily from about 3A minute to about 1 minute, although somewhat shorter or longer residence times may be employed if desired, very suitably from about 1/3 minute to about 11/3 minutes. Blending times longer than about 2 minutes are ordinarily impractical in the continuous process, although not otherwise undesirable.

The grease mixture leaving the blender is at a temperature in the range from about 10 F. to about 100 F. belo-w the solution temperature of the soap, and preferably at a temperature from about 20 F. to about 70 F. below the solution temperature of the soap. In the preparation of greases thickened twith lithium 12-hydroxystearate, the grease mixture leaving the blender is preferably at a temperature in the range from about 315 F. to about 375 F. particularly preferred conditions comprising a blender outlet temperature in the range from about 325 F. to about 365 F. in the preparation of the greases.

The grease mixture passes from the blender 35 to cooler 40 by way of line 36. Cooler 40 is an exchanger of a type providing rapid cooling together with shearing of the grease mixture. It is very suitably an exchanger of the forced film type, as described hereinabove in connection with heater 10, and is provided with a suitable cooling fluid such as water. The grease mixture is cooled in the cooler to a temperature below about 250 F., preferably below about 200 F., in less than about 1 minute, ordinarily in about 1/s to about 3%: minute.

A very advantageous method of carrying out the process in some cases involves the addition of a further amount of lubricating oil to the grease mixture from the blender before it passes into the cooler. Such additional oil may be added from storage tank 20 through line 21 and line 31 containing valve 32. This method is very advantageously employe-d in order to obtain an improved heat balance in the system when only a small amount of oil is added to the grease mixture at the blender inlet. The oil added in this manner may comprise up to about 50 percent or more of the total oil contained in the grease. Ordinarily, it `will comprise not over about 40 percent of the total oil contained in the grease. The ratio of grease mixture from the blender to this added oil may very suitably be in the range from 1:1 to about 10:1 by weight, respectively. Most advantageously, it is in the range from about 2:1 to about 5:1 by weight, respectively.

The grease mixture from the cooler passes by way of line 41 to mill 45, -which may be a mill of any suitable type employed in the grease manufacture generally, such as a Premier or Charlotte Colloid mill, set to give a clearance below about 0.01 inch. From 'mill 45, the grease mixture passes to package through line 46.

Suitable soap forming hydroxy fatty acid materials which may be employed in the production of these greases are essentially saturated hydroxy fatty acids containing l2 or more carbon atoms and one or more hydroxyl groups separated from the carboxyl group by at least one carbon atom, and the glycerides and lower alkyl esters of such acids. Such materials may be obtained from naturally occurring glycerides or produced synthetically by methods such as the hydroxylation of fatty acids or the hydrogenation of ricinoleic acid or castor oil. The hydroxy fatty acid material may be employed in the saponication in admixture with minor amounts of saponiable materials of the conventional type, as disclosed, for example, by H. V. Ashburn and O. P. Puryear in U.S. 2,450,220. The preferred saponiable materials are saturated hydroxy fatty acids containing from about 16 to 22 carbon atoms per molecule, and their glycerides and lower alkyl esters, particularly preferred materials being 12-hydroxystearic acid, the methyl ester thereof and hydrogenated castor oil. Commercial 12-hydroxystearic acids, which are included within this particularly preferred class of materials, ordinarily contain a minor proportion, such as up to about 15 percent by weight, of unsubstituted -fatty acids.

The lubricating oils employed in these greases include particularly the conventional mineral lubricating oils, having Saybolt Universal viscosities in the range from about seconds at 100 F. to about 225 seconds at 210 F., and synthetic hydrocarbon oils having viscosities in this range, such as those obtained by cracking and polymerizing products off the Fischer Tropsch process and the like. The mineral lubricating oils may be either naphthenic or paraflinic oils, or blends of different oils of these types. Other synthetic oleaginous compounds such as polyesters, polyethers, etc., having viscosities within the lubricating oil viscosity range, may also be employed in these greases as at least part of the lubricating oil component. Suitable compounds of this type include particularly the aliphatic dicarboxylic acid diesters, such as, for example, di-2-ethylhexyl sebacate, di(secondary amyl)sebacate, di-Z-ethylhexyl azelate, di-isooctyl adipate, etc. However, a lubricating oil which is substantially unreactive under the saponification conditions isy preferably employed in the saponification mixture when the process is carried out with formation of the soap-oil mixture by saponication in situ. Lubricating oils employed for this purpose are very suitably mineral oils having viscosities of at least about 150 seconds Saybolt Universal at F., preferably from about 150 to about 600 seconds at 100 F., which may be mixtures of lighter and heavier oils.

Various additives of the usual types such as corrosion inhibitors, oxidation inhibitors, extreme pressure agents, antiwear agents, etc., may be employed in these greases. Suitable oxidation inhibitors include particularly those of the amine type, such as, for example, diphenylamine, phenylalphanaphthylamine and tetramethyl 4diamino diphenyl methane. Suitable extreme pressure additives include sulfurized -fatty oils and lead soaps, which may be employed either separately or in combination. Such cornpounds may be added to the original grease mixture 6 of Table I were of the same composition as that of Example I except that they contained 6.0 percent of lithium l2-hydroxystearate, and were prepared in the same manner except for the variations shown in the table.

TABLE I.EFFECT OF HEATER OUTLET TEMPERATURE AT HIGH SOAP BASE-BLENDING OIL RATIO AND LOW BLENDING OIL TEMPERATURE Operating conditions:

Heater outlet, F Blending oil, F

ASTM Pene. at 77 F.:

Worked, 60 strokes or during cooling, ordinarily when the grease mixture, is below about 250 F.

The following example is illustrative of grease preparations carried out in accordance with this invention.

Example I A grease was prepared having the following composition in percent by weight:

The mineral lubricating oil employed in the grease was a blend comprising about 65 percent by weight of a refined residual oil having a Saybolt Universal viscosity at, 210 F. of about 160 seconds, obtained from a mixed base cnlde, and about 35 percent by weight of a refined parafiinic distillate oil having a Saybolt Universal viscosity at 100 F. of about 167 seconds.

The apparatus employed in the preparation was that shown in FIG. 1, comprising Votator heating and cooling units and a blender of the type described hereinabove.

The procedure employed was as follows. The kettle was charged with a mixture consisting of lubricating oil, 8.2 percent of lithium 12-hydroxystearate, 0.14 percent of free lithium hydroxide, and 0.6 percent by Weight of diphenylamine, based on the weight of the mixture. The mixture was heated in the kettle with stirring and with circulation from the bottom to the top of the kettle until a uniform mixture at 224 F. was obtained. It was then metered continuously at a rate of 1.8 pounds per minute to the heating Votator where it was heated to 420 F. (heater outlet temperature) in about l0.6 minute, and then passed to the blender. At the blender inlet, additional lubricating oil at 97 F. was introduced continuously into the stream of hot grease mixture at a rate of 0.4 pound per minute, and the combined stream passed through the blender with a residence time therein of about 0.85 minute. The temperature of the grease mixture at the blender outlet was 350 F. From the blender the grease mixture passed to the cooler where is was cooled in 0.5 minute to 173 F. The Votator, heater and cooler were operated with a shaft speed of 500 revolutions per minute, and the blender was operated with a shaft speed of 100 revolutions per minute. The grease mixture -from the cooler was finished by milling in a Premier Colloid mill set at 0.003 inch clearance.

The grease obtained as described above was a smooth grease of excellent appearance and very satisfactory lubricating properties generally, having an ASTM penetration at 77 F. of 231 unworked, 259 worked, -60 strokes.

The yield obtained in the above preparation was much higher than those obtained under substantially the same conditions but employing heater outlet temperatures below about 395 F., and also to those obtained in the process employing lower soap base-blending oil ratios and higher blending oil temperatures.

Table I below shows the effect of the heater outlet temperature in the above grease preparation. The greases As shown by the above data, a large increase in the grease yield, represented by 49 points in worked penetration, was obtained by increasing the heater outlet temperature from 380 F. to 410 F., employing ambient temperature blending oil and a high soap base-blending oil ratio.

The above results are presented graphically in FIG. 2 as Curve B thereof. Curve A of FIG. 2 shows the results obtained in preparations of the same grease carried out in substantially the same manner except that a blending oil preheated to 320 F. was employed, following the teachings of the Jones et al. patent referred to hereinabove, wherein a hot grease mixture was quenched by Imixing it with recycled grease mixture at about 320 F. Curve A shows that results similar to those reported in the Jones et al. patent were obtained in this process employing -a preheated blending oil at a temperature of the order of that employed by Jones et al., except that the maximum yield was obtained under these somewhat different conditions at a slightly higher temperature. Curve B shows that a maximum point in the grease yield was obtained at the same heater outlet temperature employing ambient temperature blending oil, the yield increasing sharply as the heater outlet temperature was increased to 385 F. and thereafter decreasing with increased heater outlet temperature to 390 F., similarly to Curve A. However, at heater outlet temperatures above about 390 F., the curves show an entirely different effect at further increased heater outlet temperatures up to 410 F., depending upon the blending oil temperature, an increase in the grease yield to substantially above that obtained at 385 F. being obtained -at heater outlet temperatures above about 395 F. employing an ambient temperature blending oil, as shown by Curve B.

Table II below further shows the effect of blending oil temperatures upon the grease yield in the process carried out with high heater outlet temperatures and at different soap base-blending oil ratios. The greases of this table were of the same composition as that described in Example I, and were prepared in the same manner except for the variations in operating conditions shown in the table.

TABLE IL EFFECT oF BLENDING oIL TEMPERATURE AT HIGH HEATER OUTLET TEMPERATURE AND HIGH SOAP BASE-BLENDING OIL RATIO Operating conditions:

Heater outlet, F 420 420 420 420 Blending oil F... 86 207 97 212 Blender outlet, F 318 346 750 338 Coller outlet, F 174 173 173 165 Soap base-blending wt.) 2. 25:1 225:1 4.5:1 4.5:1 Product tests:

ASTM Pene. at 77 F.:

Unworked 271 313 231 315 Worked, 60 strokes 304 335 259 351 also show that the effect upon the grease yield of employing a low temperature blending oil increases sharply with an increase in the soap base-blending oil ratio, the effect thus obtained employing a soap base-blending oil ratio of 4.5:1 being about 3 times that obtained employing a soap base-blending oil ratio of 2.25z1. In other preparations of lithium 12-hydroxystearate thickened greases, it was found that substantially no improvement in the grease yield was obtained by employing blending oils at temperatures below about 150 F. with soap base-blending oil ratios below about 2:1, respectively, and a decrease in the grease yield resulted when the heater outlet temperature was increased from 385 F. to 420 F. employing an ambient temperature blending oil at a soap base-blending oil ratio of 1.5: 1.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A continuous process for preparing lubricating greases thickened with a lithium hydroxy fatty acid soap which comprises continuously forming a molten homogeneous soap concentrateby rapidly heating in less than one minute a mixture of lithium soap comprising at least a major proportion of lithium hydroxy fatty acid soap and a portion of the lubricating oil employed in the grease to a temperature in the range from about F. to about 100 F. above the solution temperature of the soap, continuously introducing the so-heated mixture together with additional cooled lubricating oil at a temperature in the range of -150" F. into a blender operating under substantially nonshearing conditions, said mixture and said additional lubricating oil being in a ratio in about the range S11-7:1, the additional lubricating oil being continuously added in amount within the said range suicient to rapidly cool the heated mixture in less than 2 minutes to between 10 F. and 100 F. below the solution temperature of the soap, and thereafter passing the resulting grease mixture through a cooling means wherein it is cooled rapidly in less than 1 minute with shearing to a temperature below about 250 F.

2. The process of claim 1 wherein the said grease is finished by milling.

3. The process of claim 1 wherein the said soap concentrate and additional oil are employed in a ratio in about the range 3: 1-6: 1, respectively.

4. The process of claim 1 wherein the said soap concentrate and additional oil are employed in a ratio in about the range 3.5 :1-5 :1, respectively.

5. The process of claim 1 wherein the grease mixture is cooled in an exchanger of the forced film type.

6. The process of claim 1 wherein said soap concentrate and said additional lubricating oil are mixed for at least 8 about 1/3 minute under substantially nonshearing conditions.

7. T he process of claim 1 wherein the said lithium hydroxy fatty acid soap is lithium 12-hydroxystearate.

8. The process of claim 1 wherein the said lubricating oil is a mineral lubricating oil.

9. The process of claim 1 wherein the said soap concentrate comprises about 2-20 percent by weight of lithium hydroxy fatty acid soap.

10. The process of claim 1 wherein said additional oil is at a temperature in about the range -125 F.

11. A continuous process for preparing lubricating greases thickened with lithium 12-hydroxystearate which comprises continuously forming a molten homogeneous soap concentrate by rapidly heating in less than one minute a mixture of mineral lubricating oil and 2-20% by weight of lithium soap comprising at least a major proportion of lithium 12-hydroxystearate to a temperature in about the range 395 F.445 F., continuously introducing the so-heated mixture together with additional lubricating oil into a blender operating under substantially nonshearing conditions, said mixture and said additional lubricating oil being employed in a ratio in about the range 3: 1-6.5: 1, the additional lubricating oil being continuously added in amount within the range suicient to rapidly cool the heated mixture in less than 2 minutes to a temperature in the range from about 375 F. to about 315 F., and thereafter passing the resulting grease mixture through a cooling means wherein it is cooled rapidly in less than l minute with shearing to a temperature below about 250 F.

12. The process of claim 11 wherein the said soap concentrate and said additional lubricating oil are employed in a ratio in about the range 3.5: l-5.5: 1, respectively.

13. The process of claim 11 wherein the said grease is finished by milling.

14. The process of claim 11 wherein the said mixing under substantially nonshearing conditions is carried out for a period of at least about As minute.

References Cited UNITED STATES PATENTS 2,652,366 9/1953 Jones et al. 252-41 2,876,198 3/1959 Givens et al. 252-41 2,916,452 12/1959 Givens et al. 252-41 OTHER REFERENCES Manufacture and Application of Lubricating Greases, by Boner, Reinhold Pub. Corp., New York, 1954, pp. 219 and 220.

DANIEL E. WYMAN, Primary Examiner.

I. VAUGHN, Assstant Examiner.

U.S. DEPARTMENT 0F COMMERCE PATENT OFFICE Washington, D C. 20231 UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3,403,100 September 24, 1968 William R. Coons, Jr. et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as Shown below:

Column 4, line 18, "package" should read packaging Column 6, Table II, fourth column, line 3 thereof, "750" should read 350 same Table II first column, line 5 thereof, "Coller outlet, F.

should read Cooler outlet, F.

Signed and sealed this 10th day of March 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLEE, JE

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. A CONTINUOUS PROCESS FOR PREPARING LUBRICATING GREASES THICKENED WITH A LITHUM HYDROXY FATTY ACID SOAP WHICH COMPRISES CONTINUOUSLY FORMING A MOLTEN HOMOGENEOUS SOAP CONCENTRATE BY RAPIDLY HEATING IN LESS THAN ONE MINUTE A MIXTURE OF LITHIUM SOAP COMPRISING AT LEAST A MAJOR PROPORTION OF LITHIUM HYDROXY FATTY ACID SOAP AND A PORTION OF THE LUBRICATING OIL EMPLOYED IN THE GREASE TO A TEMPERATURE IN THE RANGE FROM ABOUT 10*F. TO ABOUT 100*F. ABOVE THE SOLUTION TEMPERATURE OF THE SOAP, CONTINUOUSLY INTRODUCING THE SO-HEATED MIXTURE TOGETHER WITH ADDITIONAL COOLED LUBRICATING OIL AT A TEMPERATURE IN THE RANGE OF 25-150*F. INTO A BLENDER OPERATING UNDER SUBSTANTIALLY NONSHEARING CONDITIONS, SAID MIXTURE AND SAID ADDITIONAL LUBRICATING OIL BEING IN A RATIO IN ABOUT THE RANGE 3:1-7:1, THE ADDITIONAL LUBRICATING OIL BEING CONTINUOUSLY ADDED IN AMOUNT WITHIN THE SAID RANGE SUFFICIENT TO RAPIDLY COOL THE HEATED MIXTURE IN LESS THAN 2 MINUTES TO BETWEEN 10*F. AND 100*F. BELOW THE SOLUTION TEMPERATURE OF THE SOAP, AND THEREAFTER PASSING THE RESULTING GREASE MIXTURE THROUGH A COOLING MEANS WHEREIN IT IS COOLED RAPIDLY IN LESS THAN 1 MINUTE WITH SHEARING TO A TEMPERATURE BELOW ABOUT 250*F. 